The present invention relates to a chuck. More particularly this invention concerns a locking drill chuck.
As described in my U.S. Pat. No. 5,829,761, a drill chuck has a body centered on and rotatable about an axis and formed with a plurality of angled guides opening axially forward at a front chuck end and holding respective jaws each formed with a row of teeth. The rear end of the chuck has a formation, typically a threaded bore, centered on the axis and adapted to fit with a spindle or other rotating part of a drill unit, and the front end of the chuck has a similar bore or recess which receives the tool or workpiece being rotated and into which the jaws engage. A metallic tightening ring axially fixed but rotatable about the axis on the body has a screwthread meshing with the teeth of the jaws so that rotation of the tightening ring displaces the jaws in their guides. An adjustment sleeve rotatable about the axis on the body has a metal outer part and a plastic inner part fixed on the outer part. A metallic intermediate ring fixed to the tightening ring has formations rotationally coupled to the hard outer part. The inner part rides on the intermediate ring. Mechanism is provided in the chuck for locking the tightening ring against rotation relative to the body. This mechanism is operated by cam formations inside the plastic inner ring.
The hard, normally steel, outer sleeve part is resistant to damage during normal use so that if a wrench must be applied to it, for instance, it will not be ruined. Since the intermediate ring is coupled directly to this hard outer ring, no significant torque is transmitted by the plastic part and, therefore, the adjustment ring can be actuated forcibly without damage to it. On the other hand the inner part is made of plastic which can easily be formed, for instance by molding, to have a very complex shape so as to coact with the locking mechanism and ride smoothly on the metal intermediate ring.
Assembling such a chuck is often fairly complex in that the sleeve is typically secured axially at the front end of the chuck body. In addition drilling exerts force on the sleeve that subjects it to often excessive wear. The two-part adjustment sleeve is also expensive to manufacture, and often is of such thickness that it adds unnecessarily to the overall chuck diameter.
It is therefore an object of the present invention to provide an improved drill chuck.
Another object is the provision of such an improved drill chuck which overcomes the above-given disadvantages, that is which is simple and inexpensive to manufacture and where the adjustment sleeve is protected against excessive wear.
A drill chuck has according to the invention a body centered on and rotatable about an axis and formed with an axially forwardly open tool-receiving recess and with a plurality of angled guides opening axially forward in the recess. Respective jaws axially and radially displaceable in the guides are each formed with a row of teeth. A tightening ring axially fixed but rotatable about the axis on the body has a screwthread meshing with the teeth so that rotation of the ring displaces the jaws in their guides. An adjustment sleeve rotatable about the axis on the body extends axially forward and rearward of the ring. The body has rearward of the tightening ring an outer surface directed toward an inner surface of the adjustment sleeve. Mechanism inside the adjustment sleeve couples the adjustment sleeve to the tightening ring. A support washer has an inner periphery axially fixed to the outer surface of the body and an outer periphery axially fixed to the inner surface of the adjustment sleeve. One of the peripheries is movable angularly relative to the respective surface.
Thus with this arrangement the adjustment sleeve is connected to the chuck body at the rear half of the chuck, rearward of the tightening ring. Hence many of the problems caused by attaching this sleeve at the front end of the chuck are avoided. Assembly of the chuck is simplified in that the sleeve can be slipped from the front over the chuck body and secured in place once in position. The front and middle regions of the chuck are not used for securing the adjustment sleeve in place, making these areas available for other purposes. The support washer according to the invention is axially somewhat elastically deformable, making the chuck much less susceptible to harm during normal use and more comfortable to use. Another advantage is that, when using the drill-unit motor to reverse rotate the chuck body to open the chuck while gripping the adjustment sleeve, the tendency to jam the jaws on the tightening ring is reduced by the springiness of the support washer.
According to the invention the body is further formed with an axially rearwardly open drive hole. In addition the adjustment-sleeve inner surface is formed with radially inwardly open groove receiving the washer outer periphery. The chuck has a rear end and the washer is at the rear end, spaced rearward from the ring.
The outer periphery of the washer can be is axially offset from the inner periphery. In addition the one periphery can be formed with a plurality of radially deflectable tabs. Normally the one periphery is the outer periphery and the inner surface is formed with the radially inwardly open groove in which the tabs engage. The washer is formed with axially throughgoing apertures facilitating elastic deflection of the tabs. These apertures also allow particles or grit to exit the chuck, rather than staying inside it where they would cause wear.
According to the invention the mechanism includes a locking element displaceable between an unlocked position permitting the adjustment sleeve to rotate in opposite directions about the axis relative to the body and a locked position preventing rotation of the adjustment sleeve in one of the directions relative to the body. When locked, the chuck can be tightened but not loosened. To this end the mechanism includes a cam formation on the adjustment sleeve displacing the locking element between the locked and unlocked positions. The adjustment sleeve is formed of metal of a uniform wall thickness and is formed with inwardly directed bumps or pockets forming the cam formation. Thus a shaped plastic liner is not needed, and the pockets make the surface readily grippable for use in a manually, not key-operated, chuck.
The locking system includes a coupling sleeve between the adjustment sleeve and the body, formations angularly coupling the coupling sleeve to the adjustment sleeve, the locking element angularly fixed to the coupling sleeve, and an array of teeth formed on the tightening ring and engageable with the locking element. The coupling formations include an axially extending relatively narrow finger formed on the coupling sleeve and an axially open relatively wide notch formed on the adjustment sleeve and receiving the finger. The finger is angularly limitedly displaceable in the notch. In addition the formations include an outwardly projecting spring-loaded bump on the coupling sleeve and an inwardly projecting bump on the adjustment sleeve angularly engageable and slidable past the coupling-sleeve bump. In the locked position the coupling-sleeve bump is to one side of the adjustment-sleeve bump and in the unlocked position the coupling-sleeve bump is to an opposite side of the adjustment-sleeve bump. A spring element fixed angularly to the coupling sleeve forms the coupling-sleeve bump. Another or the same spring element fixed angularly to the coupling sleeve forms the locking element.
The washer according to the invention is formed with radially extending stiffening ribs. In addition the inner surface is formed with a groove and the washer includes a snap ring set in the groove and axially engaging the outer periphery. The outer periphery is formed with a plurality of axially forwardly projecting and independently radially deflectable tabs having ends forming the outer periphery.